public class Main{
    public static void main(String[] args){
        StringBuilder sb = new StringBuilder("你好");
        System.out.println(sb);
        sb.append(1);
        sb.append(2.3);
        sb.append(true);
        sb.append("你好");
        System.out.println(sb);
        sb.reverse();
        System.out.println(sb);
        String i = sb.toString();
        System.out.println(i);
    }
}